This invention relates to an address management system for use in computers and in particular an address management system having excellent system efficiency, which permits the conversion of logical address data to a physical address data as well as an address expansion and which can be handled only by the logical address data when considered from the standpoint of software.
A variety of address systems have recently been proposed with an increase in the memory capacity of memory devices. Generally, when one program only is utilized, there is less probability that a greater memory capacity is used. For the effective utilization of bits constituting a command word an access to the main memory is effected using a short-type address. One method is a base register system using a base register capable of representing the maximum capacity of a main memory in the form of an address. In this system a displacement data designated by a command word is added to an address data designated by the register to provide an address data for a main memory. Another method is an address paging system using a main memory divided into sequentially arranged blocks each considered as a page and a page register for holding the page data. The address position designated by a command word indicates an address position in a page unless otherwise specifically indicated, and a designation bit is provided in a command word to secure a linkage between each page and to perform an indirect address function.
The base register system requires an extra time for data entry into the base register. Since in an extreme case, for example, a save/restore operation needs to be repeated for each task switching, an overhead loss arises in an Operating System OS (a control program for making the use efficiency of a whole computer system maximal). The paging system is used generally in a minicomputer and a program size is restricted dependent upon how the pages should be set. If there is a program exceeding the capacity of the page, trouble results.
In a conventional computer a central processing unit CPU, direct memory access device DMA (for example, magnetic disc device or a magnetic tape device) and main memory unit are connected directly to each other or through memory buses. In either above-mentioned system an address preparation procedure is effected only at the CPU and a physical data is directly used in the DMA. That is, since a logical address data is used in program processing and a memory access from the DMA is carried out using physical address, a complicated address management is required in the preparation of an OS.